Re:[Qemu-devel] [PATCH v2] vhost-vsock: report QMP eventwhensetrunning

[<ning.bo9@zte.com.cn>]

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> > There will be an additional problem if do this:
> > Who decides which port the `runtime` should listen?
> 
> Let the host kernel automatically assign a port using VMADDR_PORT_ANY.
> It works like this:
> 
>   struct sockaddr_vm svm = {
>       .svm_family = AF_VSOCK,
>       .svm_port = VMADDR_PORT_ANY,
>       .svm_cid = VMADDR_CID_ANY,
>   };
> 
>   int fd = socket(AF_VSOCK, SOCK_STREAM, 0);
>   ...
>   if (bind(fd, (const struct sockaddr  )&svm, sizeof(svm)) < 0) {
>       ...
>   }
> 
>   socklen_t socklen = sizeof(svm);
>   if (getsockname(fd, (struct sockaddr *)&svm, &socklen) < 0) {
>       ...
>   }
> 
>   printf("cid %u port %u\n", svm.svm_cid, svm.svm_port);
> 
> > Consider the worst case: 
> > The ports selected by two `runtime` running in parallel always conflict, 
> > and this case is unavoidable, even if we can reduce the possibility of 
> > conflicts through algorithms.
> > Because we don't have a daemon that can allocate unique port to `runtime`.
> 
> The kernel assigns unique ports and only fails if the entire port
> namespace is exhausted.  The port namespace is 32-bits so this is not a
> real-world concern.
> 
> Does this information clarify how the runtime can connect to the guest
> agent without loops or delays?

Thank you very much. I will do as you instructed above